i did!! and i did not sleep last night coz it took me 16 hrs to wait for it to finish, my classmate installed it and i dont have any idea if its correctly installed but i cant play mp4 or download Synaptic Package Manager (i dont really know what does that do but i think it will be a huge help!) what should i do? im running 12.04 ubuuntu and i updated it and upgraded it thanks!

The default package manager for the 12.04 version of Ubuntu is called "Software Center". You should be able to find it in the main menu (with all the other apps). In the software center, you can search for anything that you want to install (games, applications, libraries, etc.) and install it. That's the purpose of a package manager like Software Center or Synaptic.

For mp4 codecs, you need to install the package called ubuntu-restricted-extras (you can search for it in the software center). You can also install it by running the following command in the terminal:

$ sudo apt-get install ubuntu-restricted-extras

If you want to have Synaptic Package Manager, which is what Ubuntu used to have as its default package manager (before Software Center), you can also install it:

$ sudo apt-get install synaptic

And you should then be able to find it in the main menu along with the other apps.
The same goes for Software Center, in case it didn't install it by default (it should have):

$ sudo apt-get install software-center

For playing videos, it might be hard to make sure you have all the codecs for all the formats, what I find easiest is to just install VLC, because it will pull, along with it, pretty much all codecs (except those in ubuntu-restricted-extras), so you can install VLC:

$ sudo apt-get install vlc

As you can see from the above, the apt-get install command is a very quick and easy way to get things installed, I often prefer it to pulling up the package manager and doing all that pointing and clicking.

I'm using the line above to try and make the playlists that I export from Banshee compatible with my digital music player. When I run the sed portion of this script I'm trying to remove the portion of the path up to where ...

Here I am with English US keyboard input. But I'd like to install say Norwegian, Polish, Japanese, whatever.
I decide the easiest step. Which is to search "input". "Input Method" sounds promising. I run it.
Then I get window. That says: